JP6954491B2 - Alloy composition, method of manufacturing alloy composition, and mold - Google Patents

Description

The present invention relates to an alloy composition suitable for, for example, a mold repair material used when casting an aluminum alloy.

For example, JIS SKD61 is used as a mold used for low-pressure casting, gravity casting, and die casting of aluminum alloys. Repeated casting with the same mold will damage the mold. Melting damage and galling are known as causes of damage.
When damage occurs, the damaged part is overlaid by welding and repaired. As the repair material, an alloy having a high melting point and excellent creep resistance at high temperature and erosion resistance is preferable. An example of this alloy is disclosed in Patent Document 1.

Special Table 1-502680 Gazette

According to the alloy disclosed in Patent Document 1, since it has a high melting point and is excellent in high temperature deformation resistance, it is presumed that it will have erosion resistance to aluminum alloys. However, the alloy disclosed in Patent Document 1 is insufficient for galling, which is one of the causes of mold damage. That is, although high hardness is required for galling, the alloy disclosed in Patent Document 1 has a hardness of about 300 to 370 for HV and about 30 to 38 for HRC, and the hardness is about 30 to 38. Low.

Based on the above, the present invention provides, for example, an alloy composition and a method for producing an alloy composition, which are resistant to erosion resistance to casting of an aluminum alloy and have high hardness and can suppress the occurrence of galling, and the alloy composition. The purpose is to provide the mold used.

The present invention provides an alloy composition having an Mo-Cr-based dendritic structure and a Ni-Al-based interdendritic structure that fills the periphery of the Mo-Cr-based dendritic structure and has excellent erosion resistance and galling resistance. do.
In the alloy composition of the present invention, when the emphasis is placed on erosion resistance, the following chemical composition I is adopted to improve galling resistance due to high hardness and lower the melting point of the alloy composition. When the effect is emphasized, the following chemical composition II is adopted.
<Chemical composition I>
When Mo + Cr + Ni + Al = 100 at.%, Ni + Al = 15 to 50 at.%, Mo + Cr = 50 to 85 at.%
<Chemical composition II>
When Mo + Cr + Ni + Al = 100 at.%, Ni + Al = 40 to 70 at.%, Mo + Cr = 30 to 60 at.%

When the chemical composition I is adopted in the alloy composition of the present invention, the ratio of the area of the Mo-Cr-based dendritic structure to the entire structure is preferably 50 to 85%.
When the chemical composition II is adopted in the alloy composition of the present invention, the ratio of the area of the Mo-Cr-based dendritic structure to the entire structure is preferably 50 to 65%.
Some ranges of the chemical compositions I and II overlap. This overlapping range, that is, Ni + Al = 40 to 50 at.% And Mo + Cr = 50 to 60 at.% Is most preferable from the viewpoint of erosion resistance, improvement of hardness, and lower melting point of the alloy composition.

The alloy composition of the present invention preferably has regions having different Cr / Mo ratios in the Mo—Cr-based dendritic structure. Examples of regions in the Mo-Cr-based dendritic tissue having different Cr / Mo ratios include a form in which the Cr / Mo ratio is higher in the dendritic edge than in the central portion of the dendritic tissue.
In the alloy composition of the present invention, the maximum arm width of the Mo—Cr-based dendritic structure is preferably 50 μm or less, more preferably 10 μm or less.
In the alloy composition of the present invention, the Rockwell hardness is preferably HRC45 or higher.

The present invention comprises a simple substance metal powder of Mo, Cr, Ni or Al as a method for producing an alloy composition described above, and an alloy powder composed of two or more metals selected from Mo, Cr, Ni and Al. We propose a production method for melting and solidifying a raw material powder containing one or both of them.
Further, in the present invention, as a method for producing an alloy composition described above, a simple substance metal powder of Mo, Cr, Ni or Al and an alloy composed of two or more kinds of metals selected from Mo, Cr, Ni and Al are used. We propose a manufacturing method in which a raw material powder containing one or both of the powders is melted and solidified to form a laminate. Laminated molding is effective in refining the Mo-Cr-based dendritic structure. Further, the production method of the present invention is a raw material containing one or both of a simple metal powder of Mo, Cr, Ni or Al and an alloy powder composed of two or more metals selected from Mo, Cr, Ni and Al. It can also be applied to a method of repairing an overlay mold that melts and solidifies powder.
Further, the alloy composition of the present invention can be applied to alloy powders and alloy ingots for laminated molding.

According to the alloy composition of the present invention, the Mo-Cr-based dendritic structure mainly improves erosion resistance. In addition, the hardness is mainly increased due to the Ni-Al-based interdendritic structure. This makes it possible to obtain an alloy composition having erosion resistance and high hardness, and for example, it is possible to suppress the occurrence of galling of the mold in the casting of an aluminum alloy.

It is a photograph which shows the microstructure by the scanning electron microscope (SEM) of the alloy composition which concerns on Example of this invention. The arm width W1 of the primary tree and the arm width W2 of the secondary tree according to the present invention will be described. FIG. The figures (b) and (c) for specifying the width W2 are microstructure photographs for specifying the arm width W1 of the primary tree and the arm width W2 of the secondary tree based on the alloy composition according to the embodiment of the present invention. .. It is a figure which shows the manufacturing procedure of the alloy composition which concerns on this embodiment. It is a photograph which shows the microstructure of the sample which changed the solidification rate of the alloy composition which concerns on this Example. It is a graph which compares the hardness of the alloy composition and the conventional alloy which concerns on this Example. It is a photograph (SEM observation image) which shows the microstructure of the alloy composition (sample No. 5: ingot) which concerns on this Example. It is a photograph (SEM observation image) which shows the microstructure of the alloy composition (sample No. 6: ingot) which concerns on this Example. It is a figure which shows the result of the crystal structure analysis of the alloy composition (sample No. 5-7: ingot) which concerns on this Example by X-ray diffraction (XRD). It is a photograph (SEM observation image) which shows the microstructure of the alloy composition (sample No. 8: laminated model) which concerns on this Example. It is a photograph (SEM observation image) which shows the microstructure of the alloy composition (sample No. 9: laminated model) which concerns on this Example. The figure which shows the result of the crystal structure analysis of the alloy composition (sample No. 7: ingot, sample No. 8 and 9: laminated model) which concerns on this Example by X-ray diffraction (XRD). be. It is a figure which shows the result of having evaluated the element distribution of the dendritic structure about the alloy composition (sample No. 7: ingot) which concerns on this Example. Sample No. 8 is a TEM image obtained by observing 8 (laminated model) with a TEM (Transmission Electron Microscope). It is a result of electron diffraction in the dendritic tissue in the region A shown in FIG. Sample No. 8 is a STEM image obtained by observing the region A of 8 (laminated model) with a STEM (Scanning Transmission Electron Microscope).

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the numerical range represented by using "~" below means that the numerical values described before and after "~" are included as the lower limit value and the upper limit value. Moreover, the upper limit value and the lower limit value can be arbitrarily combined.
When used in a casting die, the alloy composition according to the present embodiment has erosion resistance and hardness that can suppress galling. These properties are obtained solely due to the tissue.

[Organization]
As shown in FIG. 1, the alloy composition 1 according to the present embodiment includes two phases, a dendritic structure 3 and an inter-dendritic structure 5. Dendrites are also referred to as dendrites.
In FIG. 1, the dendritic tissue 3 is shown in high lightness and white, and the interdendritic tissue 5 is shown in low lightness and gray. The dendritic structure 3 forms a Mo-Cr phase mainly composed of Mo and Cr, and constitutes the main phase of the alloy composition 1. The inter-tree structure 5 forms a Ni—Al phase mainly composed of Ni and Al, and constitutes a subphase responsible for curing the entire alloy. The inter-twig tissue is also called an inter-dendrite structure, an inter-columnar structure, or the like.

[Dendrite]
The dendritic structure 3 imparts erosion resistance to the alloy composition 1 according to the present embodiment.
In the dendritic structure 3, Mo has a high melting point of 2623 ° C., and if only the erosion resistance is taken into consideration, Mo alone constitutes the main phase. However, when it is used as a mold for casting, not only erosion resistance but also oxidation resistance is required. Therefore, Cr is contained in addition to Mo for the purpose of improving oxidation resistance. Cr has a melting point of 1907 ° C., which is lower than that of Mo, but it forms an extremely thin and dense protective oxide (Cr ₂ O ₃ ) on the surface and contributes to oxidation resistance.

The dendritic tissue 3 is mainly composed of a body-centered cubic (bcc) structure, but partially has a B2 ordered phase. The B2 regular phase is a regular phase mainly composed of Ni and Al.
In the dendritic structure 3, the higher the amount of Mo, the higher the erosion resistance, and the higher the amount of Cr, the higher the oxidation resistance. The ratio of Mo and Cr may be determined according to the required characteristics. That is, the ratio of Mo may be increased when erosion resistance is particularly required, and the ratio of Cr may be increased when oxidation resistance is particularly required. However, in the dendritic structure 3, oxidation resistance can be obtained even if Cr is added in a small amount. The dendritic structure 3 mainly contains a Mo-Cr-based solid solution containing a large amount of the upper two elements of Mo and Cr, and contains Ni and Al contained in the interdendritic structure 5 and unavoidable impurities. It does not prevent that. Hereinafter, in the present specification, the dendritic tissue may be referred to as a Mo—Cr-based dendritic tissue. As shown in Examples described later, the Mo-Cr dendritic structure should not be interpreted as containing only Mo and Cr, and the inclusion of elements such as Al and Ni is permitted.

In the Mo-Cr-based dendritic tissue 3, Cr is concentrated in the edge portion of the dendritic tissue, and the Cr concentration at the edge is high. This appears in FIG. 1 where the edges of the primary and secondary tree arms are darkened. The dendritic edge is a connecting region between the inter-twig tissue and the dendritic tissue, and it is desirable that the composition is inclined in order to maintain the continuity of the tissue. The fact that the composition is inclined and has continuity between the inter-dendritic structure and the dendritic structure means that the properties such as erosion resistance, oxidation resistance, and high hardness of each of Mo, Cr, Ni, and Al are continuously inclined. That is, it means that the characteristic difference depending on the place is unlikely to occur. The concentration distribution of each element in the dendritic tissue can be evaluated by EPMA (Electron Probe Micro Analyzer). First, a mirror-polished sample is prepared, and a surface analysis is performed on a region (for example, 50 μm × 50 μm) in which the dendritic tissue sufficiently enters. The obtained analysis result is converted into a concentration display. A line analysis evaluation is performed at an arbitrary position so as to cross the dendritic tissue, and the element distribution is evaluated. The Cr / Mo ratio is calculated at the edge of the tree branch and the center of the tree branch, respectively. In the alloy composition of the present invention, when the Cr / Mo ratio of the tree edge portion and the tree branch center portion was compared, it was confirmed that the Cr / Mo mass ratio (weight ratio) of the tree branch edge portion was higher than that of the tree branch center portion. .. In this way, the element distribution inside the dendritic tissue can be evaluated. At the edge, the Cr content ratio increased and the Ni and Al contents also increased. Solid solution strengthening or precipitation strengthening of NiAl at the tree branch edge is effective as an Al erosion resistant alloy.
The B2 ordered phase existing in the dendritic tissue mainly composed of bcc can be confirmed by high-magnification observation by TEM (Transmission Electron Microscope). The observation sample can be used for TEM observation by cutting out a test piece having a thickness of about 100 nm by, for example, a microsampling method using a Focused Ion Beam (FIB). In the TEM observation, selected area diffraction of φ200 nm is performed aiming at the dendritic structure, and from the analysis result of the obtained electron diffraction image, the diffraction pattern showing the bcc structure and the spot of the slightly present B2 ordered phase can be identified. Further, when the dark field image is imaged according to the spot of the B2 regular phase, the distribution state of the B2 regular phase can be confirmed. In the alloy composition of the present invention, it has been confirmed that a granular B2 ordered phase having a size of about 100 nm exists (see FIG. 15). It is considered that these existences contribute to the increase in hardness and the high softening resistance in the alloy composition of the present invention.

[Inter-twig tissue]
Next, the inter-twig structure according to the present embodiment imparts mechanical strength, particularly hardness, to the alloy composition according to the present embodiment. Hardness is required to accommodate the galling that occurs during casting.
The inter-twig structure 5 is composed of a solid solution or an intermetallic compound mainly composed of Ni and Al. The interdendritic structure 5 is preferably composed of a NiAl intermetallic compound containing Ni and Al in a ratio of approximately 1: 1. This intermetallic compound has a body-centered cubic (bcc) structure and a B2-type crystal structure similar thereto. These intermetallic compounds are excellent in high temperature strength and oxidation resistance, and are suitable for dies for casting aluminum alloys. The melting point of the NiAl intermetallic compound is 1638 ° C., and the hardness is approximately HRC41. In addition to NiAl, Ni ₃ Al can also form an intermetallic structure 5 containing Ni and Al by an intermetallic compound having an L12-type ordered structure with good symmetry using a face-centered cubic crystal as a basic lattice. The hardness of Ni ₃ Al is approximately HRC44. There are several types of Ni-Al intermetallic compounds, for example, the hardness of _{Ni 2} Al _{3 is about HRC62.} These intermetallic compounds are produced in the laminating molding process and do not change significantly even when exposed to a temperature range of about 500 ° C. to 700 ° C. Therefore, when the alloy composition of the present application is applied to a mold in which an Al molten metal of about 700 ° C. is repeatedly adhered, the hardness of the alloy composition does not change, that is, the softening resistance is high and the hardness is maintained. NS. In short, since the alloy composition of the present application has a stable structure even at 700 ° C., it is unlikely to change with respect to repeated loading at this temperature, and its hardness hardly decreases even when it is used for a long period of time. This is also an advantageous feature over conventional materials.
For example, SKD61 is a typical conventional material applied to an Al die casting mold. In fact, SKD61 is often used with a hardness exceeding 40 HRC, but in most cases it is tempered to 45 HRC by heat treatment. Since the tempering temperature at this time is about 600 ° C. to 650 ° C., the SKD61 base material itself causes softening when the molten Al at 700 ° C. exceeding the tempering temperature repeatedly adheres. Therefore, a nitriding treatment (for example, a nitriding treatment for improving the surface layer of 50 to 200 μm to about 800 to 1000 Hv) may be performed on the surface of the SKD61 base material, but when applied to an Al die casting mold, it is repeated. There is a problem that the nitriding layer gradually disappears due to the influence of heat, and finally the SKD61 base material is softened.
The intermetallic structure 5 mainly contains a Ni—Al-based intermetallic compound having a high content of the upper two elements of Ni and Al, and Mo and Cr and unavoidable impurities contained in the dendritic structure 3 and the like. It does not prevent the inclusion of. Hereinafter, in the present specification, the inter-twig tissue may be referred to as a Ni—Al-based inter-twig tissue. As shown in Examples described later, the Ni-Al-based interdendritic structure should not be interpreted as containing only Ni and Al, and the inclusion of trace amounts of elements such as Mo and Cr is permitted.

As shown in FIG. 1, the inter-dendritic tissue 5 exists so as to fill the space between the Mo-Cr-based dendritic tissues 3. Since the inter-twig structure 5 contains Al, it is preferable that the amount occupying the alloy composition is small from the viewpoint of erosion resistance. However, in order to cope with galling, it is preferable that the hardness of the material constituting the mold is high. Therefore, in the present embodiment, hardening by forming a Ni—Al-based inter-twig structure 5 is utilized. The hardness of the alloy in this embodiment is preferably higher than the hardness of SKD61 used as the base material of the mold before heat treatment for the purpose of improving galling resistance. That is, the alloy in this embodiment is HRC45 or more, further 50 or more, preferably HRC55 or more. If the hardness is too high, the toughness is lowered, so the upper limit is HRC70, preferably HRC65 or less.

[Ratio of main phase and sub-phase]
In the alloy composition according to the present embodiment, when importance is attached to erosion resistance, the ratio of the area of the dendritic structure 3 to the entire alloy is preferably 50 to 85%.
If the area ratio of the dendritic structure 3 is less than 50%, sufficient erosion resistance may not be obtained. The erosion resistance is greatly affected by the ratio of the area occupied by the dendritic tissue 3, but is also affected by the degree of fineness of the dendritic tissue 3. That is, the finer the dendritic structure 3, the better the erosion resistance. On the other hand, if the area ratio of the dendritic structure 3 exceeds 85%, the inter-dendritic structure 5 as a hardened phase may be reduced, and sufficient hardness may not be obtained. The hardness is also greatly affected by the ratio of the area occupied by the inter-dendritic tissue 5, but is also affected by the degree of fineness of the dendritic tissue 3. That is, even if the composition is the same, the finer the dendritic structure 3, the higher the hardness.
As described above, in consideration of erosion resistance and hardness, the ratio of the area occupied by each of the dendritic structure 3 and the inter-twig structure 5 is changed by changing the composition ratio of the raw material, changing the cooling rate at the time of modeling, and the like. It is preferable to adjust.
The ratio of the area occupied by the dendritic structure 3 to the entire alloy can be obtained by polishing the cross section of the alloy to a mirror surface, performing SEM observation, converting the SEM image into two gradations, and then deriving the SEM image.
In the alloy composition according to the present embodiment, when hardness and melting point reduction are more important than erosion resistance, the ratio of the area occupied by the dendritic structure 3 to the entire alloy is preferably 50 to 65%. That is, when the ratio of the area occupied by the dendritic structure 3 to the entire alloy is 50 to 65%, the ratio of the area occupied by the interdendritic structure 5 as the cured phase to the entire alloy is 35 to 50%. It is easy to obtain sufficient hardness. Further, since Mo, which is the main component of the dendritic structure 3, has a high melting point, the melting point of the alloy composition can be lowered by setting the ratio of the area occupied by the dendritic structure 3 to the entire alloy to 50 to 65%. ..

[Arm width of dendritic tissue]
As described above, the finer the dendritic structure, the better the erosion resistance. Further, the finer the dendritic tissue, the higher the hardness. In the present embodiment, the degree of fineness in the dendritic tissue shall be specified by the arm width of the dendritic tissue.
FIG. 2A shows a modeled dendritic crystal. In the dendritic crystal, a primary branch that can be said to be a trunk is first formed, and then a secondary tree that can be said to be a branch is formed on the primary branch so as to be orthogonal to its axis. In the present embodiment, preferably, the maximum arm widths W1 and W2 of the dendritic tissue composed of the primary and secondary branches are both 50 μm or less. The more preferable maximum arm widths W1 and W2 are 30 μm or less, the further preferable maximum arm widths W1 and W2 are 20 μm or less, and the further preferable maximum arm widths W1 and W2 are 10 μm or less. For the maximum arm width W1, the maximum value of the width in the direction orthogonal to the extension direction of the primary tree branch arm can be obtained as the maximum arm width W1 in the field of view of the SEM image imaged at a magnification of 300 times. Similarly, for the maximum arm width W2, the maximum value of the width in the direction orthogonal to the extension direction of the secondary tree branch arm is obtained as the maximum arm width W2 in the field of view of the SEM image imaged at a magnification of 300 times. Can be done.

FIG. 2B shows the arm widths W1 and W2 in the sample No. 1 of the example described later. The maximum arm width W1 of sample No. 1 is about 20 μm, and the maximum arm width W2 is about 45 μm. Hereinafter, the maximum arm widths W1 and W2 may be simply referred to as arm widths W1 and W2.
FIG. 2C shows a microstructure photograph of Sample No. 4 of Example described later, and it can be seen that both the arm width W1 and the arm width W2 are 10 μm or less. As described above, the structure of sample No. 4 is finer than that of sample No. 1. From the two photographs of FIGS. 2 (b) and 2 (c), if the arm widths W1 and W2 of the dendritic tissue are small, that is, if the dendritic tissue is fine, the inter-dendritic tissue that fills the space between the dendritic crystals is also fine. It turns out to be. This means that even if the ratio of the dendritic structure to the inter-dendritic structure in the entire alloy is the same, if the arm widths W1 and W2 are reduced, the individual dendritic structure and the inter-dendritic structure are reduced. means.

As described above, when MoCr and NiAl are compared, the erosion resistance of NiAl is inferior. Here, if the Ni-Al-based interdendritic structure is made finer, the area contributing to erosion is reduced and only a part of the surface layer is eroded, resulting in a reduction in the amount of elution, resulting in an alloy composition. As a whole, the resistance to erosion is improved. As described above, such miniaturization of the structure also leads to an improvement in hardness, which contributes to an improvement in erosion resistance and hardness necessary for suppressing mold damage.

Here, it is known that erosion is caused by the following two mechanisms.
・ Physical erosion (cavitation erosion)
Melt loss occurs when the molten metal is suddenly accelerated and cavitation occurs at the part where the shape suddenly changes inside the mold. Cavitation is a physical phenomenon in which bubbles are generated and disappear in a short time due to a pressure difference in a liquid flow. Since the stress caused by the pressure impact generated when the bubbles disappear acts to mechanically damage the surface, it is effective to improve the strength of the surface as a measure against damage. That is, it can be said that the improvement of hardness is effective for erosion resistance.
・ Chemical erosion (dissolution due to compound formation)
When the molten aluminum alloy comes into contact with the mold surface, aluminum diffuses and the aluminum alloy is welded to the mold surface. The surface portion of the welded mold falls off together with the welded aluminum alloy. For such chemical erosion, it is effective to apply a material having low reactivity with aluminum. That is, it is effective to apply a material that does not have a eutectic point with aluminum and has a high melting point.

Next, the chemical composition I and the chemical composition II of the alloy composition having the structure described above will be described.
The chemical composition I has a larger total amount of Mo and Cr than the chemical composition II (the upper limit of Mo + Cr is 85 at.%), And is a composition that emphasizes erosion resistance.
The chemical composition II has a larger total amount of Ni and Al than the chemical composition I (the upper limit of Ni + Al is 70 at.%). The chemical composition II is a composition that emphasizes the effects of improving galling resistance due to high hardness and lowering the melting point of the alloy composition.
When the amount of Ni + Al is large, the hardness of the alloy composition according to the present embodiment is high, but the erosion resistance may be low. When the amount of Mo + Cr increases, the erosion resistance of the alloy composition according to the present embodiment increases, but the hardness decreases and the melting point increases. Based on these tendencies, the chemical compositions I and II can be appropriately adopted depending on the production method and application of the alloy composition.
[Chemical composition I of alloy composition]
Ni + Al = 15 to 50 at.% Mo + Cr = 50 to 85 at.%
When Mo + Cr + Ni + Al = 100at.%
Ni: 7.5-25 at.% Al: 7.5-25 at.%
Cr: 10-25 at.% Remaining: Mo and unavoidable impurities

The amount of Ni + Al affects the amount of inter-twig tissue. That is, when the amount of Ni + Al is 15 at.% Or more, hardness for suppressing mechanical damage is imparted. When the amount of Ni + Al is more than 50 at.%, The amount of the dendritic structure mainly composed of Mo and Cr, which is responsible for erosion resistance, is reduced. Therefore, Ni + Al is preferably 15 to 50 at.%. The content of Ni + Al is more preferably 20 to 45 at.%, More preferably 30 to 45 at.%.

Each of Ni and Al can be contained in the range of 7.5 to 25 at.%. If the content of each is less than 7.5 at.%, The amount of inter-twig tissue may be small and the hardness may be insufficient. Further, when the content exceeds 25 at.%, The amount of the dendritic structure composed of Mo and Cr decreases, and the erosion resistance may be insufficient.
The respective amounts of Ni and Al are more preferably 10 to 25 at.%, More preferably 15 to 25 at.%, And even more preferably 20 to 25 at.%.

Next, the amount of Mo + Cr affects the erosion resistance. That is, if the amount of Mo + Cr is less than 50 at.%, The amount of dendritic tissue mainly responsible for erosion resistance is small. If the amount of Mo + Cr exceeds 85 at.%, The melting point of the raw material becomes high, and there is a concern that the following problems may occur. In addition, the amount of inter-twig tissue 5 responsible for precipitation hardening is reduced. Therefore, Mo + Cr is preferably 50 to 85 at.%. The content of Mo + Cr is more preferably 50 to 80 at.%, And even more preferably 50 to 70 at.%.
<Problems when the amount of Mo + Cr exceeds 85 at.% And the melting point of the raw material becomes high>
-As will be described later, the alloy powder according to this embodiment can be produced, for example, by an atomizing method. During atomization, which is a powder manufacturing process, it is difficult to control the composition of the molten metal because the raw material having a high melting point does not dissolve well and undissolved residue is generated in the crucible.
Even if the alloy powder could be produced by the atomization method, even if the obtained alloy powder was irradiated with laser light to perform laminated molding, melting, defoaming, and deposition were difficult to proceed sufficiently, and defects were contained. There is a high possibility that a model will be formed. In other words, even if a raw material having a high melting point in which the amount of Mo + Cr exceeds 85 at.% Can be atomized, the powder will have poor formability.
・ Even if the output of the high-frequency melting furnace is increased and the high-melting point raw material is melted, the crucible (generally, alumina, zirconia, etc.) cannot withstand and is damaged at that temperature, and the hot water does not reach the hot water. , The alloy cannot be obtained. Further, even if the damage to the crucible can be avoided, the temperature of the path from the crucible to the hot water nozzle must be kept high, so that the power consumption is large. If the temperature of the hot water nozzle portion is low, problems such as clogging when hot water is discharged occur.

Cr is contained in the range of 10 to 25 at.%, And Mo is defined as the balance of the entire alloy minus Ni, Al and Cr. If the Cr content is less than 10 at.%, The oxidation resistance may be insufficient, and if it exceeds 25 at.%, The amount of Mo responsible for erosion resistance is reduced. That is, when the erosion resistance is emphasized, the Mo content may be increased, and when the oxidation resistance is emphasized, the Cr content may be increased. As the Cr content is increased, the melting point gradually decreases.
A more preferable amount of Cr is 12 to 20 at.%, And a more preferable amount of Cr is 12 to 18 at.%.

C, B, and Si form hard particles such as carbides, borides, and borides with Mo, Cr, Ni, and Al while lowering the melting point of the alloy, and contribute to the improvement of wear resistance. Si is also a chemical component added as a deoxidizing material, and has the effect of improving the cleanliness of the molten metal. The contents of C, B and Si are 0.01 at. The effect is exhibited at% or more, but 8.0 at. If it is added in excess of%, the amount of hard particles increases and cracks are likely to occur during laminated molding. Therefore, when C, B, and Si are positively added in the chemical composition I, 0.01 to 8.0 at. %.

[Chemical composition II of alloy composition]
The chemical composition of the alloy composition preferably has the following composition when it is important to improve the galling resistance and lower the melting point of the raw material.
Ni + Al = 40 to 70 at.% Mo + Cr = 30 to 60 at.%
When Mo + Cr + Ni + Al = 100at.%
Ni: 20-35 at.% Al: 20-35 at.%
Cr: 10-50 at.% Remaining: Mo and unavoidable impurities

When hardness is important, the amount of Ni + Al that affects the amount of inter-twig structure is 40 at.% Or more. However, when the amount of Ni + Al is more than 70 at.%, The amount of Mo—Cr-based dendritic tissue mainly responsible for erosion resistance decreases. Therefore, in order to have both desired hardness and erosion resistance, Ni + Al is preferably 40 to 70 at.%.
In the chemical composition II, the content of Ni + Al is more preferably 40 to 65 at.%, Further preferably 40 to 55 at.%.

Each of Ni and Al can be contained in the range of 20 to 35 at.%. By containing Ni and Al in this range, the hardness can be HRC50 or higher.
In the chemical composition II, the respective amounts of Ni and Al are more preferably 20 to 30 at.%, And even more preferably 20 to 25 at.%.

The amount of Mo + Cr that affects the erosion resistance is 30 to 60 at.% In the chemical composition II. If the amount of Mo + Cr is less than 30 at.%, The amount of dendritic tissue mainly responsible for erosion resistance is small, and it becomes difficult to obtain desired erosion resistance. On the other hand, when the amount of Mo + Cr exceeds 60 at.%, The amount of inter-twig tissue 5 decreases. Therefore, when hardness is important, the upper limit of the amount of Mo + Cr is preferably 60 at.%.
In the chemical composition II, the content of Mo + Cr is more preferably 35 to 60 at.%, Further preferably 40 to 60 at.%.

Cr is contained in the range of 10 to 50 at.%, And Mo is defined as the balance of the entire alloy minus Ni, Al and Cr. If the Cr content is less than 10 at.%, The oxidation resistance may be insufficient, and if it exceeds 50 at.%, The amount of Mo responsible for erosion resistance is reduced. That is, when the erosion resistance is emphasized, the Mo content may be increased, and when the oxidation resistance is emphasized, the Cr content may be increased.
As described above, as the Cr content is increased, the melting point gradually decreases, but the Cr content is 50 at. When it reaches about%, the melting point starts to rise again. Therefore, when lowering the melting point of the alloy composition is emphasized, the more preferable amount of Cr is 15 to 45 at.%, And the more preferable amount of Cr is 20 to 40 at.%. Advantages of lowering the melting point of the alloy composition include the following.
<Advantages of lowering the melting point of alloy compositions>
-The alloy powder according to this embodiment can be produced, for example, by an atomizing method. When the melting point of the raw material is lowered, the raw material dissolves well in the crucible in a short time during atomization, so that it is easy to obtain a molten metal having a uniform composition, and the hot water can be discharged without being clogged with the hot water nozzle. -If the raw material can be melted at a low temperature, the life of the crucible will be extended, and the production cost will be reduced.
-In the case of laminated modeling using atomized powder, the raw material melts without remaining undissolved due to the output of general laser light, and defoaming and deposition proceed, so it is easy to form a model without defects. In other words, the powder produced by atomizing a raw material having a low melting point has good formability.

C, B, and Si form hard particles such as carbides, borides, and borides with Mo, Cr, Ni, and Al while lowering the melting point of the alloy, and contribute to the improvement of wear resistance. Si is also a chemical component added as a deoxidizing material, and has the effect of improving the cleanliness of the molten metal. The contents of C, B and Si are 0.01 at. The effect is exhibited at% or more, but 8.0 at. If it is added in excess of%, the amount of hard particles increases and cracks are likely to occur during laminated molding. Therefore, even in the chemical composition II, when C, B, and Si are positively added, 0.01 to 8.0 at. %.

As described above, the chemical compositions I and II can be appropriately adopted depending on the production method and application of the alloy composition.
Some ranges of the chemical compositions I and II overlap. This range, that is, Ni + Al = 40 to 50 at.% And Mo + Cr = 50 to 60 at.% Is most preferable from the viewpoint of erosion resistance, improvement of hardness, and lower melting point of the alloy composition.

[Form of alloy composition, manufacturing method]
The alloy composition according to the present embodiment is used, for example, as an alloy ingot or a laminated model as described below, or an alloy powder for obtaining the same. As an example, the alloy powder is also used as a raw material for the powder overlay method, which is a kind of additive manufacturing method.
The method for producing the alloy composition of the present embodiment comprises a simple substance metal powder composed of at least one of Mo, Cr, Ni and Al, and at least two metals selected from Mo, Cr, Ni and Al. A production method in which a raw material powder containing one or both of the alloy powders is melted and solidified can be used. The elemental metal powder may be one kind, two kinds, or more, and the alloy powder may be one kind or two kinds. As a specific example, a mixture of Mo powder and Cr powder, which are elemental metal powders, and NiAl powder, which is an alloy powder, can be used as a raw material alloy. _{Alternatively, a mixture of Ni 3} Al, which is an alloy powder, and a MoCr alloy can be used as a raw material alloy. Since Mo and Cr are completely solid-solved, the composition of the MoCr alloy can be freely adjusted. Since the CrMo alloy containing a large amount of Cr has a low melting point, it is easy to trigger the formation of a molten pool.
The ratio of Cr in the MoCr alloy is 80 to 90 att. When it becomes% (that is, the ratio of Mo is 10 to 20 at.%), The melting point of the MoCr alloy is the lowest, and becomes about 1700 ° C. It is as follows that it is easy to create a trigger for forming a molten pool. When the MoCr alloy having a low melting point is irradiated with laser light, melting is started from this composition powder. Since the liquefied MoCr alloy has an active metal surface and increases fluidity, it increases the contact area while getting wet with the surrounding NiAl powder, transfers heat, and also alloys at this contact part to lower the melting point. It causes conversion and easily promotes melting. Mixing the composition powder having a low melting point in this way improves the ease of forming the molten pool and the stability. Therefore, by mixing the CrMo alloy containing a large amount of Cr and the NiAl powder, stable formation of the molten pool is possible, and the formability can be improved.
Further, in the manufacturing method of the present embodiment, it is important to have a melting and solidifying step in the process, and an example thereof will be described below.

[Manufacturing method of alloy powder]
An example of a method for producing this alloy powder will be described with reference to FIG.
The gist of this production method is that an alloy powder is obtained by granulating a raw material powder using a spray dryer and then firing it.

This manufacturing method includes a raw material preparation step S101, a raw material mixing step S103, a granulation step S105, a firing step S107, and an alloying step S109.
In the raw material preparation step S101, for example, Mo powder, Cr powder, Ni powder and Al powder are prepared as raw materials according to the composition of the alloy composition to be obtained. The raw material is not limited to the metal powder as a simple substance, and may be, for example, MoCr alloy powder, NiAl alloy powder, or Mo powder, Cr powder, and NiAl alloy powder. The particle size of these raw material powders may be appropriately selected according to the particle size of the alloy powder to be obtained.

Next, in the raw material mixing step S103, the raw material powder prepared in the raw material preparation step S101 is wet-mixed with a wax such as paraffin. For mixing, a known device, for example, an attritor can be used, and in addition to the raw material powder and wax, for example, ethanol as a dispersion medium can be added to the attritor and wet-mixed to obtain a slurry of the mixed powder. can.

Next, in the granulation step S105, the slurry obtained in the raw material mixing step is sprayed and dried by a spray dryer to granulate the powder of the mixture.

Next, in the firing step S107, the powder of the mixture granulated in the granulation step S105 is put into a drying furnace, degreased at a degreasing temperature of 400 ° C. or higher and 600 ° C. or lower, and then fired at a firing temperature of 600 ° C. or higher. The degreasing temperature is a temperature at which the wax used can be removed, and the firing temperature is a temperature for solidifying the powder particles of the mixture. In the granulated powder that has undergone firing, the raw material powders are adhered to each other, but they are not alloyed.

Next, in the alloying step S109, the granulated powder that has undergone the firing step S107 is exposed to a temperature higher than the firing temperature in the firing step S107 to alloy. For this alloying, for example, thermal plasma-droplet-refining (PDR) that is passed through a high temperature region such as plasma can be used. By the alloying treatment using PDR, the granulated powder is instantly melted and solidified. Alternatively, after the firing step S107, for the purpose of alloying, the contact portion between the powders can be alloyed by further raising the temperature. This powder has the strength to be used for laminated molding.

Here, thermal plasma is an ionized gas in which molecules in the gas are dissociated into atomic states by applying energy to the gas, and the atoms are further ionized into ions and electrons, and metal pieces are heated by an electric furnace. Compared with the conventional manufacturing method, it is possible to heat the temperature to a very high temperature, specifically, a temperature of 5000 ° C. or higher in a high temperature portion. In the thermal plasma that forms an extremely high temperature atmosphere in this way, even a powder having a high melting point such as Mo can be dissolved instantly.

In addition, since the thermal plasma can locally generate an extremely high temperature atmosphere, a steep temperature gradient can be formed between the thermal plasma region and the surrounding atmosphere. Due to this rapid temperature gradient, the metal pieces are instantly melted in the high temperature part of the thermal plasma and become spherical due to their own surface tension. The spheroidized metal pieces can be quickly cooled below the melting point by the surrounding atmosphere and solidified to form metal spheres.

By the above steps, the alloy powder according to this embodiment is produced. In this way, the granulated powder solidified by removing the wax through the firing step S107 is instantly heated in the alloying step S109 to melt and solidify. As a result, the dendritic structure of the obtained alloy powder is fine. Further, in the obtained alloy composition, each particle has a shape close to a true sphere due to surface tension, and the particle surface becomes smooth.

[Other powder manufacturing methods]
The alloy powder according to this embodiment can be produced by an atomizing method. In the atomizing method, the molten metal is scattered as droplets and solidified by the kinetic energy of the high-pressure spray medium to produce a powder. It is classified into applicable spray media, water atomization method, gas atomization method, jet atomization method, etc. Any atomizing method can be adopted for producing the alloy powder according to the present embodiment. The alloy powder obtained by the atomizing method is also melted and solidified, and the solidification rate is high, so that the dendritic structure can be made fine.

In the water atomization method, the molten metal is allowed to flow down from the bottom of the dundish, high-pressure water is sprayed onto the molten metal flow as a spray medium, and the molten metal is sprayed by the kinetic energy of the water. The water atomization method has a faster cooling rate during solidification than other atomization methods. However, the obtained powder has an irregular shape.
In the gas atomization method, a high-pressure gas, for example, an inert gas such as nitrogen or argon or air is used as the spray medium. The powder produced by gas atomization tends to be spherical. It is understood that the main reason for this is that the cooling rate by gas is smaller than that of water, and the molten particles formed as droplets are spheroidized by surface tension before solidifying.
In the jet atomization method, a combustion flame such as kerosene is used as a spray medium, and a high-speed and high-temperature frame jet exceeding the speed of sound is injected into the molten metal, and the molten metal is accelerated and crushed over a relatively long time. This powder tends to be spherical, and a finer particle size distribution can be obtained.
The EiGA method (electrode-induced dissolved gas atomizing method) is a method in which an ingot is prepared, used as an electrode material, melted by an induction coil, and directly atomized. Since MoCr and NiAl have different melting points, they may separate in an atomizing furnace depending on the composition. In this case, an ingot is prepared in a furnace with a large stirring force and the EIGA method is applied to make it homogeneous. A powder of composition can be obtained.

The method for producing an alloy powder described above is an example in the present invention, and the present invention can produce an alloy powder by another production method.

[Manufacturing method of alloy ingot]
Most typically, the alloy ingot can be obtained by a melting / casting method in which molten metal is obtained in a melting furnace and then poured into a predetermined mold to solidify. Melting furnaces include a furnace that converts electrical energy into thermal energy and melts it, an electric resistance furnace that uses Joule heat, a low-frequency induction furnace that uses electromagnetic induction current, a high-frequency induction furnace that uses eddy current, and an arc melting furnace. and so on.
The alloy ingot obtained by the melting / casting method has a shape according to the shape of the mold, and can take various shapes such as a flat plate shape and a rectangular parallelepiped shape.

The alloy ingot according to the present embodiment includes a member formed by the additive manufacturing method. In the additive manufacturing method referred to here, the raw material powder is melted and solidified to form a solidified layer. This operation is repeated to form a member having a predetermined shape by laminating solidified layers, and has a concept including powder overlay. For example, with respect to an aluminum alloy casting die, the alloy composition according to the present embodiment can be powder-stacked to repair a damaged portion. This repaired portion constitutes the alloy ingot according to the present embodiment.

For the powder overlay, for example, plasma powder overlay welding and laser powder overlay welding can be used.
Plasma powder overlay welding uses plasma as a heat source. Since plasma powder overlay welding is performed in an inert argon atmosphere, an overlay layer having a smooth surface and few pores can be formed inside.
Laser powder overlay welding uses a laser as a heat source. Laser powder overlay welding has the advantage that it can overlay thin objects because the heat input region can be narrowed. Further, in laser powder overlay welding, since the region where the temperature is raised is small, the temperature gradient with the base material becomes large, and after the laser beam passes through, the temperature drops sharply and the temperature is rapidly cooled. Therefore, since it is melted and solidified, it is advantageous for the miniaturization of the dendritic structure.
Laser Metal Deposition (LMD) can be used for laser powder overlay welding. LMD forms a build-up layer on the surface of the base material by supplying the raw material powder while irradiating the base material with laser light.

As the raw material powder for powder overlay, alloy powder produced by the above-mentioned method or a method other than the above-mentioned method can be used.
Further, if it is a powder overlay welding machine capable of supplying a plurality of types of powder, Mo powder, Cr powder, Ni powder and Al powder can be used as raw materials, and MoCr alloy powder and NiAl alloy powder can be used as raw materials. You can also do it. In this case, the raw material powder is alloyed by melting and solidifying during overlaying. With this method, the inclined composition can be obtained from the base material to the surface. The inclined composition can be said to be a composition in which the ratio of hardness and composition differs from the base material to the surface by changing the ratio of the base material component, MoCr, and NiAl. Eliminating the difference in hardness between the base material and the molding material (that is, the overlay alloy material) leads to reduction of cracks between the base material and the base material. Further, when erosion resistance and galling resistance are required on the surface portion in adjacent regions on the surface, different ratios of MoCr and NiAl can be added to each region. In this way, it is possible to form a built-up alloy with different compositions for the parts that require erosion resistance and the parts that require galling resistance, and to obtain a high-performance mold with excellent wear resistance. can.

[Use]
As an application using the composition of the present invention, it is suitably used as a repair material for a mold for casting an aluminum alloy. For example, it is used as a mold for a low-pressure casting mold for molding an aluminum wheel and a mold for an aluminum cylinder head of an engine. It is also widely applied to other members that are required to withstand high temperatures. For example, it can be applied to a bearing or the like in which frictional heat can be generated by high-speed rotation.
Further, the method for producing an alloy composition of the present invention can also be applied to a method for repairing an overlay mold.

[Example 1]
Next, an example of the present invention will be described based on examples.
The following four types of raw material powders were prepared and mixed so as to have the following alloy composition.
Mo powder: particle size 3-8 μm
Cr powder: particle size 1-5 mm
Ni powder: particle size 8 to 15 mm
Al powder: particle size 40 μm or less Alloy composition:
Mo; 45 at.% Cr; 15 at.% Ni; 20 at.% Al; 20 at.%

After melting the above raw material powder in a high-frequency induction melting furnace, an alloy mass was obtained. This molten and cast alloy ingot is designated as Sample No.1. When the liquidus temperature of Sample No. 1 was determined, it was 1630 ° C. The liquidus temperature is a value calculated by Thermo-calc (thermodynamic database: SSOL6).
Sample No. 2 is an alloy ingot that has been heat-treated to hold it at 1200 ° C. for 2 hours.
Further, the molten and cast alloy ingot was partially remelted and solidified by irradiating it with a laser beam. The conditions for remelting are as follows. The alloy ingot having a slower scanning speed is referred to as sample No. 3, and the alloy ingot having a faster scanning speed is referred to as sample No. 4.
Sample No. prepared in Example 1. The sizes of 1 to 4 are 20 mm in diameter and 50 mm in length.

Remelting conditions Equipment: IPG YLR-2000-S 2kW fiber laser Output: 1200W
Side gas: Ar
Laser light incident angle: 10 °
Laser light scanning width: 13 mm
Laser light scanning speed: 100 mm / min (Sample No. 3)
500 mm / min (Sample No. 4)

Samples Nos. 1, 3 and 4 were microstructured with a scanning electron microscope. The result is shown in FIG. Regarding Samples Nos. 3 and 4, the portion that was remelted and solidified was observed. The same applies to hardness.
Further, the Vickers hardness of Samples Nos. 1 to 4 and the conventional alloy was measured by a Vickers hardness tester at room temperature with a load of 1000 gf and a holding time of 15 seconds. The measurement was performed 10 times, and the average value of 8 points excluding the maximum value and the minimum value was recorded. The measured Vickers hardness (HV) was converted to Rockwell hardness (HRC). For conversion, ASTM (American)
Society for Testing and Materials) E140 Table 2 was referenced. The result is shown in FIG. The conventional alloy is DENSIMET 185 by Plansee, Austria. DENSIMET is a registered trademark of Plansee.

The tissue observation position and the measurement position of the arm width are on the cross section of the sample, that is, on the two-dimensional surface. If the sample is an alloy ingot, cut out a sample with a cross section for observation and measurement from the center of the ingot. In the case of remelting / solidification (Samples No. 3 and No. 4), a cross section parallel to the scanning direction of the laser was formed, and the cross section was observed after polishing. In addition, the reflected electron image was taken, and the arm widths W1 and W2 of the primary and secondary twigs were obtained from the dendritic tissue and the inter-twig tissue. For the arm width of the primary tree, the maximum width in the growth direction of the dendritic tissue was measured. The arm width of the secondary tree was measured at any 10 locations and used as an average value. As shown in FIG. 4, it can be seen that all of Samples Nos. 1, 3 and 4 have a complex structure of a dendritic tissue and an inter-dendritic tissue. This structure is observed by the difference in contrast due to the difference in composition. Here, the reflected electron image was converted into two gradations, and the area ratio of each color was derived by image analysis software. First, as a result of observing the structure, the structure becomes finer in the order of Sample Nos. 1, 3 and 4. This is due to the cooling rate during solidification. That is, the sample No. 1 obtained by casting after melting in a high-frequency induction melting furnace has a slower cooling rate during solidification than local remelting and solidification by irradiation with laser light. Further, regarding sample No. 3 and sample No. 4, the faster the scanning speed of the laser beam, the faster the cooling rate at the time of solidification. Therefore, the structure of sample No. 4 is larger than that of sample No. 3. It is fine. The measurement results of the arm widths W1 and W2 of Sample Nos. 1, 3 and 4, respectively, were as follows.
Sample No. 1: W1 = 20 μm, W2 = 30 μm, area ratio of dendritic tissue = 68%
Sample No. 3: W1 = 6 μm, W2 = 10 μm, area ratio of dendritic tissue = 62%
Sample No. 4: W1 = 6 μm, W2 = 4 μm, area ratio of dendritic tissue = 70%

Next, as shown in FIG. 5, all of Samples Nos. 1 to 4 according to this example have a hardness of HRC50 or more, and except for Sample No.2, they have a hardness of HRC55 or more. ing. Therefore, when Samples Nos. 1 to 4 according to this example are used as a repair material for an aluminum alloy casting die, they show high resistance to galling. This is because the area ratio of the dendritic structure is less than 85%, and the hard layer Ni-Al-based inter-dendritic structure is finely present. In particular, Samples Nos. 3 and 4, whose structures have been refined by remelting and solidification, have a hardness of HRC60 or higher and exhibit excellent resistance to galling.
Further, from Sample No. 1 and Sample No. 2, the hardness of the alloy composition of the present embodiment can be adjusted by subjecting it to high temperature heat treatment.

The composition of the dendritic tissue and the inter-dendritic tissue of Sample No. 1 was analyzed by Energy Dispersive X-ray Spectroscopy (EDX). The results are as follows.
Dendrite:
Mo; 72.2 at.% Cr; 24.6 at.%
Ni; 1.8 at.% Al; 1.4 at.%
Intertree structure Ni; 49.9 at.% Al; 45.2 at.%
Mo; 0.8 at.% Cr; 4.1 at.%

From the results of the above composition analysis, it is recognized that the interdendritic structure is mainly composed of a NiAl intermetallic compound having a composition ratio of Ni and Al of 1: 1.

[Example 2]
Sample No. 1 except that the raw material powder prepared in Example 1 was mixed so as to have the following three types of alloy compositions. An alloy ingot was obtained in the same procedure as in 1. These melted and cast alloy ingots are designated as Samples Nos. 5, 6 and 7. Sample No. prepared in Example 2. The sizes of 5 to 7 are 20 mm in diameter and 50 mm in length.
Alloy composition of sample No. 5:
Mo; 15 at.% Cr; 35 at.% Ni; 25 at.% Al; 25 at.%
Alloy composition of sample No. 6:
Mo; 10 at.% Cr; 50 at.% Ni; 20 at.% Al; 20 at.%
Alloy composition of sample No. 7:
Mo; 19 at.% Cr; 19 at.% Ni; 28 at.% Al; 34 at.%

[Comparison example]
As a comparative example, the raw material powder prepared in Example 1 was used and mixed so as to have the following alloy composition. Using this mixed powder, sample No. An attempt was made to obtain an alloy ingot by the same procedure as in No. 1, but the alloy ingot could not be obtained because it could not be melted in the high frequency induction melting furnace.
Mo; 65 at.% Cr; 25 at.% Ni; 5 at.% Al; 5 at.%

[Sample No. 1, 5-7, consideration of comparative examples]
For Samples Nos. 5, 6 and 7, and Comparative Example 1, the liquidus temperature was determined by Thermo-calc (thermodynamic database: SSOL6). For Samples Nos. 5 to 7, Rockwell hardness (HRC) was determined in the same manner as above. The results are summarized in Table 1.

As shown in Table 1, Samples No. 5 to 7 have a lower liquidus temperature than Sample No. 1, and the melting point of the alloy composition is lowered.
In particular, for sample No. 5 (liquidus line temperature: 1505 ° C.), the liquidus line temperature is 125 ° C. higher than that of sample No. 1 (liquidus line temperature: 1630 ° C.) while obtaining a hardness of 55 HRC or higher. Low. Therefore, the amount of Cr is increased as compared with Mo, and the amount of Ni + Al is 50 at. %, The amount of Mo + Cr is 50 at. % Is effective in achieving both desired hardness and lower melting point of the alloy composition.
Next, when sample No. 1 and sample No. 6 are compared, the amount of Ni + Al in both samples is 40 at. %, The amount of Mo + Cr is 60 at. However, the liquidus temperature of sample No. 6 (Mo: 10 at.%, Cr: 50 at.%) Is higher than that of sample No. 1 (Mo: 45 at.%, Cr: 15 at.%). Low. Therefore, when it is important to improve the oxidation resistance by containing Cr and lower the melting point of the alloy composition, the Cr content may be set to be larger than the Mo content. According to Sample No. 6, a hardness of 50 HRC or more can be obtained while keeping the liquidus temperature at 1550 ° C. or lower.
Comparing Sample No. 5 (Ni + Al = 50 at.%) And Sample No. 7 (Ni + Al = 62 at.%), Sample No. 5 has a lower liquidus temperature and is harder than Sample No. 7. It's also expensive. Therefore, the upper limit of the total amount of Ni and Al is 70 at. %, And even 60 at. %, More preferably 50 at. It turned out to be%.
The total amount of Mo and Cr is 90 at. %, The total amount of Ni and Al is 10 at. In Comparative Example 1, which is%, the liquidus temperature was as high as 2130 ° C., melting in a high-frequency induction melting furnace could not be performed, and an alloy ingot could not be obtained. From this result, the upper limit of the total amount of Mo and Cr is 85 at. %, The lower limit of the total amount of Ni and Al is 15 at. %, Should be. The upper limit of the total amount of Mo and Cr is preferably 80 at. %, More preferably 70 at. %, More preferably 60 at. %. The lower limit of the total amount of Ni and Al is preferably 20 at. %, More preferably 30 at. %, More preferably 40 at. %.

In the same procedure as in Example 1, the arm widths W1, W2 and the area ratio of the dendritic tissue of Sample Nos. 5, 6 and 7 were measured. The measurement results were as follows.
Sample No. 5: W1 = 11 μm, W2 = 9 μm, area ratio of dendritic tissue = 58%
Sample No. 6: W1 = 17 μm, W2 = 11 μm, area ratio of dendritic tissue = 66%
Sample No. 7: W1 = 8 μm, W2 = 7 μm, area ratio of dendritic tissue = 57%
Table 2 shows the measurement results for sample No. 1 and the measurement results for samples Nos. 5, 6 and 7.

The SEM observation image of sample No. 5 is shown in FIG. 6, and the SEM observation image of sample No. 6 is shown in FIG. 7, respectively.
As shown in FIGS. 6 and 7, it can be seen that Samples Nos. 5 and 6 also have a complex structure of dendritic tissue and inter-dendritic tissue.
Further, by comparing FIG. 6 and FIG. 7, it can be seen that the structure of sample No. 5 (FIG. 6) is finer than that of sample No. 6 (FIG. 7). This corresponds to the result that the arm widths W1 and W2 shown in Table 2 are both smaller in sample No. 5. Further, as shown in Table 1, Sample No. 5 has a larger amount of Ni + Al and higher hardness than Sample No. 6. This is because sample No. 5 has a higher proportion of Ni-Al interdural structure in the alloy composition than sample No. 6, and Ni-Al system contributes to the improvement of hardness in the fine structure. This is because the inter-tree tissue is appropriately dispersed.

The crystal structure of Sample Nos. 5 to 7 was analyzed by X-ray diffraction (XRD). The result is shown in FIG.
As shown in FIG. 8, it was confirmed that the bcc phase and the NiAl (B2) phase were mixed in the samples Nos. 5 to 7.
Of the samples Nos. 5 to 7, the total amount of Ni and Al is 62 at. Sample No. 7, which has the highest percentage, has the highest peak intensity of the NiAl (B2) phase. However, as shown in Table 1, the sample No. 7 is more than the sample No. 7. 5 (Ni + Al = 50 at.%) Has higher hardness. From this result, it was found that the hardness correlates not only with the ratio of the Ni—Al interdendritic structure in the alloy composition but also with the miniaturization of the structure. It is presumed that the finer the structure of the alloy composition and the more appropriately dispersed the Ni—Al inter-twig structure, the more advantageous it is in obtaining high hardness.

[Example 3]
In Example 3, two laminated shaped bodies were produced by laminated molding by laser metal deposition (LMD) (Sample Nos. 8 and 9).
Sample No. The sizes of 8 and 9 are 4 mm × 20 mm × 40 mm. In the following, the laminated model may be simply referred to as a model.

The following four types of raw material alloy powders for laminated modeling were prepared. A melting raw material of this raw material powder was prepared and melted using a normal high-frequency vacuum melting furnace to prepare a mother alloy, which was prepared by a gas atomization method in an argon atmosphere. A powder having a particle size of 53 to 150 μm was classified from the atomized powder and used for addition production. The d10, d50, and d90 of the classified powder are d10: 58 μm, d50: 92 μm, and d90: 148 μm, respectively.
Sample No. Alloy composition of 8 and 9:
Mo; 19 at.% Cr; 19 at.% Ni; 28 at.% Al; 34 at.%

Laminated molding conditions Equipment: Overlay welding by Lasertec65 Laser Metal Deposition (LMD) manufactured by DMG Mori Seiki Co., Ltd. Base material: Alloy718
Laser light scanning speed: 1000 mm / min
Raw material powder supply: 14 g / min
Laser light output: 1.6 kW (Sample No. 8)
2.0kW (Sample No. 9)

[Sample No. 8 and 9 (modeled body) and sample No. Consideration about 7 (Ingot)]
The liquidus temperature and Rockwell hardness (HRC) of Samples Nos. 8 and 9 were determined in the same manner as in Examples 1 and 2. The results were obtained from the sample No. 2 prepared in Example 2. Table 3 shows the results of 7 (ingot).

As shown in Table 3, since the alloy compositions of Samples Nos. 7 to 9 are the same, the liquidus temperature is 1540 ° C. The alloy composition of Samples Nos. 7 to 9 falls within the range of Chemical Composition II, but according to Chemical Composition II, the liquid phase is obtained while obtaining a hardness of 45 HRC or more, further around 50 HRC or 50 HRC or more. The linear temperature could be 1600 ° C. or lower, further 1550 ° C. or lower. That is, it was confirmed that the chemical composition II is also an effective composition when an alloy composition is produced by the additive manufacturing method.
The ingot (Sample No. 7) and the modeled body (Sample No. 8) were heat-treated (heat treatment conditions: held at 700 ° C. for 10 hours in a vacuum) to determine the hardness after the heat treatment. The results are shown in Table 3. The "hardness after heat treatment" was obtained by converting the Vickers hardness (HV) measured by the same method as described above into the Rockwell hardness (HRC). Comparing the "hardness" and "hardness after heat treatment" in Table 3, there is almost no change in hardness before and after the heat treatment, and the sample before the heat treatment and the sample after the heat treatment have the same hardness. It was confirmed. That is, with this alloy composition, it is considered that the softening resistance was high because the structure formed in the solidification process was stable at a high temperature. That is, the alloy composition within the range of the chemical composition II is considered to be suitable for a member requiring heat resistance, for example, a member such as a die casting mold in which Al erosion is likely to occur.

The SEM observation image of sample No. 8 (laser light output: 1.6 kW) is shown in FIG. 9, and the SEM observation image of sample No. 9 (laser light output: 2.0 kW) is shown in FIG.
In addition, the arm widths W1 and W2 and the area ratio of the dendritic tissue measured for Sample No. 8 and Sample No. 9 are shown in Table 4 together with the results of Sample No. 5 to 7. The methods for measuring the arm widths W1 and W2 are as shown in the first embodiment. The area ratio of the dendritic structure for Samples Nos. 8 and 9 was observed after polishing the cross section (side surface of the laminated model) parallel to the modeling direction.

As shown in FIGS. 9 and 10, it can be seen that the samples Nos. 8 and 9 prepared by the additive manufacturing method also have a composite structure of a dendritic structure and an inter-dendritic structure.
By comparing FIG. 9 and FIG. 10, it can be seen that the structure of sample No. 8 (FIG. 9) is finer than that of sample No. 9 (FIG. 10). This is because sample No. 8 (laser light output: 1.6 kW), which has a small laser light output, has a faster cooling rate than sample No. 9 (laser light output: 2.0 W), and is therefore finer. This is because dendritic tissue (dendrite) is formed.
Further, FIGS. 6 (sample No. 5, ingot) and FIG. 7 (sample No. 6, ingot) shown in the section of Example 2 and FIG. 9 (sample No. 8, laminated model) of this example. And by comparison with FIG. 10 (Sample No. 8, laminated model), it was confirmed that the structure of the laminated model was significantly finer than that of the ingot. This is the sample No. shown in Table 4. Arm widths W1 and W2 of 8 and 9 (modeled body) and sample No. This is supported by a comparison with arm widths W1 and W2 of 1,5 to 7 (ingot). Sample No. obtained by casting solidification. In 1, 5 to 7 (ingot), the range of the arm width W1 is 8 to 20 μm, the range of the arm width W2 is 7 to 30 μm, and the dendritic tissue becomes thick. On the other hand, the sample No. obtained by the laminated molding. In 8 and 9, the arm widths W1 and W2 can both be suppressed to 10 μm or less, and further to 6 μm or less. Sample No. With respect to 8, the arm widths W1 and W2 can both be suppressed to 3 μm or less. As a result, the mean free path of the Ni—Al inter-twig structure becomes smaller, so that the regions with low erosion resistance are small and dispersed, and local erosion does not occur. As a result, it is considered that the erosion resistance of the entire alloy composition is enhanced. That is, the Mo-Cr dendritic structure having high erosion resistance exists in a network shape, and the Ni-Al dendritic structure having lower erosion resistance than the Mo-Cr dendritic structure is formed so as to fill the space between them. Since it exists, the sample No. obtained by the laminated molding. It is presumed that 8 and 9 have improved erosion resistance.

Sample No. which is a modeled body. The area ratio of the dendritic tissue of Nos. 8 and 9 (Sample No. 8: 59%, Sample No. 9: 56%) was determined by Sample No. It is lower than the area ratio (68%) of the dendritic tissue of 1 (ingot). However, as described above, since the laminated model has a very fine dendritic structure, the sample No. Sample Nos. 8 and 9 (modeled body) are No. It is considered that the same erosion resistance as 1 (ingot) can be obtained.
As described above, sample No. The liquidus temperature of 1 (ingot) is 1630 ° C., whereas the sample No. 1 (ingot) has a liquidus temperature of 1630 ° C. The liquidus temperature of 8 and 9 (modeled body) is 1540 ° C. That is, the sample No. Sample Nos. 8 and 9 are the sample numbers. The liquidus temperature is 90 ° C. lower than 1. Such a low melting point of the alloy composition is advantageous when applying the alloy composition to a layered manufacturing method such as laser metal deposition (LMD). When the temperature of the alloy composition to be modeled is high, the temperature of the molten pool during modeling is high, that is, the temperature difference from room temperature is large and the amount of shrinkage generated during cooling is large, so that the modeled object is liable to crack. .. Since the temperature difference is small when the melting point is lowered, it is not easily affected by the heat shrinkage that occurs after molding, and stable molding becomes possible. This is because the formation of beads welded to each other proceeds smoothly.
Further, in order to lower the melting point of the alloy composition, the raw material is melted without remaining undissolved by the output of general laser light, and defoaming and deposition proceed, so that it is easy to form a model without defects.

By Energy Dispersive X-ray Spectroscopy (EDX), Sample No. The composition of 8 and 9 dendritic tissues and inter-dendritic tissues was analyzed. The results are as follows.
From the results of EDX, it was found that the dendritic structure also contained Ni and Al. In addition, it was confirmed that Mo was almost absent in the inter-twig tissue, but a small amount of Cr was present.
Sample No. prepared in Example 1. The result of EDX of 1 (ingot) and the sample No. prepared in this example. Comparing the EDX results of 8 and 9 (modeled body), the modeled body has a larger amount of Al and Ni present in the dendritic tissue. Therefore, it is considered that the B2 ordered phase mainly composed of Ni and Al also exists in the dendritic structure in the modeled body. The consideration of the B2 regular phase will be described later.
<Sample No. 8>
Dendrite:
Mo; 46.7 at.% Cr; 33.1 at.%
Ni; 4.4 at.% Al; 15.8 at.%
Intertree structure Ni; 47.0 at.% Al; 49.7 at.%
Mo; 0.5 at.% Cr; 2.8 at.%
<Sample No. 9>
Dendrite:
Mo; 53.4 at.% Cr; 29.3 at.%
Ni; 2.8 at.% Al; 14.5 at.%
Intertree structure Ni; 47.7 at.% Al; 49.7 at.%
Mo; 0 at.% Cr; 2.6 at.%

FIG. 11 is a diagram showing the results of crystal structure analysis of samples Nos. 8 and 9 prepared in this example by XRD. In addition, FIG. 11 also shows the result of XRD of sample No. 7 having the same composition as samples No. 8 and 9.

As shown in FIG. 11, it was confirmed that the bcc phase and the NiAl (B2) phase were mixed in the samples No. 8 and 9 as well as the sample No. 7.
Since the compositions of Samples Nos. 7 to 9 were the same, the peak positions of the bcc phase and the NiAl (B2) phase did not differ significantly between the samples.
However, when comparing Sample No. 8 and Sample No. 9, the maximum peak intensity of the bcc phase and NiAl (B2) phase is higher in Sample No. 8 (laser light output: 1.6 kW), which has a smaller laser light output. big.

FIG. 12 shows the sample No. The result of evaluating the elemental distribution of the dendritic tissue for 7 (ingot) is shown.
The results of surface analysis by EPMA are shown in the left figure of FIG. JXA8500F manufactured by JEOL Ltd. was used for the surface analysis by EPMA. The analysis conditions are acceleration voltage: 15 kV, irradiation current: 0.02 A, beam diameter: φ0.1 μm, step size: 0.2 μm, irradiation time: 30 msec, number of spots: 250 × 250 points, and a range of 50 μm × 50 μm. A surface analysis was performed. The elemental distribution of the dendritic tissue was evaluated by converting the obtained analysis result into a concentration display and performing a line analysis evaluation at an arbitrary position so as to cross the dendritic tissue.
As a result, as shown in the right figure of FIG. 12, the sample No. It was confirmed that in the dendritic tissue of No. 7, there were regions where the Cr / Mo ratio was different between the dendritic edge portion and the dendritic center portion. Sample No. When this analysis and evaluation was performed on No. 7, the Cr / Mo ratio in the central portion was about 0.4, while there was a region in the edge portion where the Cr / Mo ratio was 0.6 or more.
Further, the right figure of FIG. 12 shows that Al and Ni are also contained in the Mo-Cr-based dendritic structure.
Sample No. Sample No. 7 having the same chemical composition as 7. For 8 (modeled body), sample No. The elemental distribution of the dendritic tissue was evaluated in the same manner as in No. 7 (Ingot). As a result, the sample No. It was confirmed that even in the dendritic tissue of No. 8, there are regions where the Cr / Mo ratio is different between the dendritic edge portion and the dendritic center portion. Sample No. As for No. 8, the Cr / Mo ratio in the central portion was about 0.4, while there was a region in the edge portion where the Cr / Mo ratio was 0.6 or more.

In order to evaluate the microstructure in the dendritic tissue, high-magnification observation was performed by TEM (Transmission Electron Microscope) (magnification: 3000 times). FIG. 13 shows the sample No. The TEM image of 8 (laminated model, before heat treatment) is shown. In FIG. 13, the dark gray region is the dendritic tissue, and the light gray region is the interdendritic tissue.
FIG. 14 shows the result of electron diffraction in the dendritic tissue in the region A of FIG. From the analysis result of the electron diffraction image, the main phase of the dendritic tissue could be identified as the bcc structure, but a spot of the B2 ordered phase was slightly confirmed in the dendritic tissue.
The conditions for electron diffraction are as follows.
Device model: Hitachi High-Tech Co., Ltd. Model HF-2100
Acceleration voltage: 200kV
Selected area diffraction method Selected field: φ200 nm

FIG. 15 shows the sample No. 8 is a STEM image obtained by observing the region A of 8 (laminated model) with a STEM (Scanning Transmission Electron Microscope). The left side is a bright field image (BF-STEM image), and the right side is a dark field image (DF-STEM image). The dark-field image is imaged after being adjusted so that the B2 ordered phase diffraction shown in FIG. 14 occurs.
From the dark field image of FIG. 15, it can be seen that the B2 ordered phase is distributed as a granular structure of about 100 nm. It is considered that the hardness of the dendritic tissue was improved due to the presence of such fine precipitates. Since this B2 ordered phase is stable even in a high temperature environment of about 700 ° C. used in the Al die casting type, as shown in Table 3, the sample No. It is probable that 8 (laminated model) had a high softening resistance with almost no change in hardness before and after the heat treatment at 700 ° C.
The TEM and STEM sample preparation procedures and observation conditions are as follows.
<Procedure for preparing TEM and STEM samples>
Sample No. One surface of 8 (laminated model) was polished to prepare a test piece having a thickness of about 100 nm by a microsampling method using a Focused Ion Beam (FIB). For microsampling, FB-2100 type manufactured by Hitachi High-Tech Co., Ltd. was used. <Conditions for TEM and STEM observation>
Sample thickness: 100 nm
Device model: Hitachi High-Tech Co., Ltd. Model HF-2100
Acceleration voltage: 200kV

Although the preferred embodiments and examples of the present invention have been described above, other than the above, the configurations listed in the above embodiments may be selected or appropriately changed to other configurations as long as the gist of the present invention is not deviated. It is possible to do it.

1 Alloy composition 3 Dendrite structure 5 Intertree structure W1 Arm width of primary tree W2 Arm width of secondary tree

Claims (12)

Mo-Cr dendritic tissue and
The fill around the Mo-Cr-based dendritic tissue, and the tissue between the Ni-Al-based dendritic, an alloy composition Ru provided with,
The alloy composition contains Ni: 7.5 to 25 at.%, Al: 7.5 to 25 at.%,
Cr: 10 to 25 at.%, Remaining: Mo and unavoidable impurities,
When Mo + Cr + Ni + Al = 100at.%
Ni + Al = 15 to 50 at.%, Mo + Cr = 50 to 85 at.%,
With the ratio of the surface product of the Mo-Cr-based dendritic organization accounted the entire tissue is 50 to 85%
The Rockwell hardness of the alloy composition is HRC45 or higher.
Alloy composition.
Mo-Cr dendritic tissue and
The fill around the Mo-Cr-based dendritic tissue, and the tissue between the Ni-Al-based dendritic, an alloy composition Ru provided with,
The alloy composition contains Ni: 20 to 35 at.%, Al: 20 to 35 at.%,
Cr: 10 to 50 at.%, Remaining: Mo and unavoidable impurities,
When Mo + Cr + Ni + Al = 100at.%
Ni + Al = 40 to 70 at.%, Mo + Cr = 30 to 60 at.%,
With the ratio of the surface product of the Mo-Cr-based dendritic organization accounted the entire tissue is 50 to 65%
The Rockwell hardness of the alloy composition is HRC45 or higher.
Alloy composition.
Mo-Cr dendritic tissue and
The fill around the Mo-Cr-based dendritic tissue, and the tissue between the Ni-Al-based dendritic, an alloy composition Ru provided with,
The alloy composition contains Ni: 7.5 to 25 at.%, Al: 7.5 to 25 at.%,
Cr: 10 to 25 at.%, Remaining: Mo and unavoidable impurities,
When Mo + Cr + Ni + Al = 100at.%
Ni + Al = 15 to 50 at.%, Mo + Cr = 50 to 85 at.%,
In the Mo-Cr dendritic tissue, there are regions with different Cr / Mo ratios, and
The Rockwell hardness of the alloy composition is HRC45 or higher.
Alloy composition.
Mo-Cr dendritic tissue and
The fill around the Mo-Cr-based dendritic tissue, and the tissue between the Ni-Al-based dendritic, an alloy composition Ru provided with,
The alloy composition contains Ni: 20 to 35 at.%, Al: 20 to 35 at.%,
Cr: 10 to 50 at.%, Remaining: Mo and unavoidable impurities,
When Mo + Cr + Ni + Al = 100at.%
Ni + Al = 40 to 70 at.%, Mo + Cr = 30 to 60 at.%,
In the Mo-Cr dendritic tissue, there are regions with different Cr / Mo ratios, and
The Rockwell hardness of the alloy composition is HRC45 or higher.
Alloy composition.
The Cr / Mo ratio in the Mo-Cr dendritic tissue is higher in the dendritic edge than in the central part of the dendritic tissue.
The alloy composition according to claim 3 or 4.
Ni + Al = 40 to 50 at.%, Mo + Cr = 50 to 60 at.%,
The alloy composition according to any one of claims 1 to 5.
The maximum arm width of the Mo-Cr dendritic tissue is 50 μm or less.
The alloy composition according to any one of claims 1 to 6.
The maximum arm width of the Mo-Cr dendritic tissue is 10 μm or less.
The alloy composition according to any one of claims 1 to 7.
Rockwell hardness is HRC 50 or higher,
The alloy composition according to any one of claims 1 to 8.
Claimed by melting and solidifying a single metal powder of Mo, Cr, Ni or Al and a raw material powder containing one or both of an alloy powder consisting of two or more metals selected from Mo, Cr, Ni and Al. The alloy composition according to any one of claims 1 to 7 and 9 is produced.
Method for producing alloy composition.
Laminated molding by melting and solidifying a single metal powder of Mo, Cr, Ni or Al, and a raw material powder containing one or both of an alloy powder consisting of two or more metals selected from Mo, Cr, Ni and Al. The alloy composition according to any one of claims 1 to 6, 8 and 9 is produced.
Method for producing alloy composition.
A mold using the alloy composition according to any one of claims 1 to 9 as a repair material.

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